MKGradientPolylineRenderer
A visual representation of any polyline overlay object with a gradient.
Declaration
class MKGradientPolylineRendererOverview
This renderer only applies a stroke to the line; it doesn’t fill it. Set the gradients with setColors:atLocations: and pair colors to locations that MapKit represents as unit distance values along the distance of the polyline. Don’t subclass MKGradientPolylineRenderer. Use the class as-is.
The gradient displays itself along the direction of the line.